Systems exist for firing a projectile to disable or destroy a stationary or moving target; some of these systems fire a guided projectile, and others of these systems fire an unguided projectile.
An example of a guided-projectile system is a submarine torpedo system, which fires a guided intercept torpedo from a launch tube to disable or destroy a target such as an enemy submarine, an enemy ship, or an incoming torpedo. Before firing the intercept torpedo, an operator maneuvers the submarine such that the launch tube, and thus the intercept torpedo within the tube, are aimed at the target. But because the intercept torpedo is a guided projectile, a guidance subsystem, which is disposed on the intercept torpedo and/or on the submarine and which monitors the location of the target using, e.g., sonar, can steer the intercept torpedo toward the target even after the intercept torpedo leaves the launch tube. Therefore, the guidance subsystem can correct the intercept torpedo's trajectory if the launch tube was inaccurately aimed at the target when the intercept torpedo was fired from the tube, if the intercept torpedo's trajectory is altered by an unaccounted for force (e.g., a current), or if the target changes course. Another example of a guided-projectile system is the ground-based Patriot® missile system, which aims an intercept missile at an incoming missile, fires the intercept missile, and, using phased-array radar, steers the fired intercept missile toward the incoming missile.
An example of an unguided-projectile system is a ship-board gun system, which fires an unguided shell to disable or destroy a target such as an enemy ship or aircraft. Before the gun fires the shell, an operator maneuvers the gun turret such that gun barrel, and thus the shell within the barrel, are aimed at the target. Because the shell is an unguided projectile, the gun cannot correct or otherwise affect the trajectory of the shell once the shell exits the barrel.
Guided- and unguided-projectile systems each have desirable features. For example, a guided projectile, such as a torpedo, is relatively small and can be unmanned, and an unguided projectile, such as a shell, is often relatively inexpensive to manufacture and maintain.
But unfortunately, guided- and unguided-projectile systems also have undesirable features.
Because a guided projectile, such as a torpedo, typically includes relatively complex subsystems, such as guidance, steering, power, and propulsion subsystems, a guided projectile is often relatively expensive to manufacturer and maintain. Furthermore, because a guided projectile is typically destroyed when it strikes a target, it is typically not reusable. Consequently, guided-projectile systems are often relatively expensive to maintain and operate because each time a guided projectile is launched, the projectile must be replaced.
Furthermore, an unguided-projectile system, such as a gun, often cannot be carried by an unmanned vehicle. For example, to accurately aim a ship-board gun barrel at a moving target, the gun's ranging subsystem computes the proper direction and azimuth of the gun barrel by executing a targeting algorithm that often accounts for the following factors: the temperature, wind velocity, and other weather conditions, the position, velocity, and acceleration of the ship on which the gun is located, the position, velocity, and acceleration of the target, and the strike location of one or more previously fired shells. Because the targeting algorithm is so complex, the ranging subsystem often includes a relatively large computer subsystem that consumes a significant amount of power and that requires significant peripheral services (e.g., cooling). Moreover, the shell loading/unloading subsystem is often unsuitable for an underwater unmanned vehicle, because the water may corrode or otherwise damage components of the loading/unloading subsystem. In addition, the “jerking” motion that the recoil of a ship-board gun may impart to an unmanned vehicle may have undesirable consequences. For example, the recoil may damage the vehicle, or turn the vehicle such that the ranging subsystem must re-aim the gun before firing the next round. Consequently, the relatively large sizes of the computer subsystem and power supply and gun-recoil affects may render an unguided-projectile system unsuitable for an unmanned vehicle. Furthermore, the lack of a suitable projectile loading/unloading subsystem may render an unguided-projectile system unsuitable for an unmanned underwater vehicle.
Moreover, there are few, if any, unguided projectiles that are suitable for firing underwater. Because water is denser than air, unguided projectiles, such as bullets and shells, designed for above-water targets often experience significant drag in water, and thus often have a limited underwater range of a few tens of meters.